Sister and brother Molly and Josh (who constantly annoy each other) are to spend the summer with their Grandparents. Upon arrival however, they receive a less than warm welcome. Grandad Bill is at best illusive and his sister Great aunt Maude is just plain horrible! Once settled in to their new home they try to avoid the house as much as possible. Ending up in the shed at the bottom of the garden the two children accidentally enter a secret code, whilst idly playing around with the bench vice. The floor descends into the depths of the earth, finally coming to rest in a deep subterranean bunker/ laboratory where they find their Granddad working on his big secret… Building an army of robot insects to battle a “Silent invasion of alien insects trying to wipe out Earth’s delicate ecosystem starting with bees. Now the game is up they discover their grandad isn’t horrible at all. He was just pretending to keep them away from his shed and possible danger. They swear to keep his secret safe as long as they can help him.